exam Maths Puzzle Numerical Ability

I am solving the following equation:

sqrt x-1 = x-3

I get 5 but then I did it again and got 2. HELP!

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exam Other Question
Factor completely: 9x^2 + 12xy + 4x^2 -25

My solution to this problem was (3x+2y)-25

I am not too confident that this is correct. If this is not correct could you assist me with this problem please. Thanks. Subtract

4x/x-5-
20/x-5